Come in handy
A lot of English expressions come from the vocabulary of body parts.
Here’s another one using HAND
Come in handy (verb)
if something “comes in handy” it means that it is useful for something that you want to do.
– I always keep some pasta in the kitchen cupboard, it comes in handy if I want to make a quick meal.
– Mobile phones come in handy for meeting up with friends when you go out at night
– A little notebook in my pocket comes in handy for writing my ideas, before I forget.